1. Field of the Invention
The present invention relates to a pulse wave detecting apparatus which presses a pulse wave sensor against an arterial vessel of a living body or subject via body surface above the artery and detects a pressure pulse wave produced from the artery.
2. Related Art Statement
There is known a pulse wave detecting device including (a) a pulse wave sensor having a press surface and including a plurality of pressure sensing (PS) elements provided in one or more arrays in the press surface, the pulse wave sensor being adapted to be pressed against an arterial vessel of a living subject via a body surface of the subject such that a direction of the array or arrays of PS elements intersects a direction of extension of the artery, so that each of the pressure sensing elements detects a pressure pulse wave produced from the artery and generates a pulse wave signal representing the detected pulse wave, (b) a pressing device which produces a pressing force to press the press surface of the pulse wave sensor against the artery via the body surface, and (c) regulating means for continuously changing the pressing force of the pressing device applied to the pulse wave sensor, determining an optimum value of the pressing force based on one or more of the pulse wave signals generated from the PS elements, and holding the pressing force of the pressing device at the thus determined optimum value. The prior apparatus reads in the pulse wave signal or signals supplied from one or more of the PS elements pressed with the optimum pressing force, and obtains the pressure pulse wave of the subject based on the pulse wave signal or signals. The prior apparatus is disclosed in, for example, Japanese Patent Application laid open for inspection purpose under Publication No. 1(1989)-285244.
However, in the prior pulse wave detecting device, the condition of pressing of the pulse wave sensor against the body surface (e.g., manner of contact of the former with the latter) may change due to, for example, motion of the subject (e.g., motion of his or her wrist on which the sensor is being worn). In this event, the reading or detected magnitude of the pulse wave is adversely affected. The detected pulse wave may contain both change due to natural change of blood pressure of the subject and change due to artificial change of the pressing condition of pulse wave sensor. Thus, the accuracy of detection of the prior device is not satisfactory.